Transparent impact-resistant molded articles

ABSTRACT

A molded article obtained by blow molding a propylene having a substantially syndiotactic structure or a resin composition comprising a polypropylene having a substantially syndiotactic structure and a copolymer of ethylene and propylene, and a multi-layer molded article obtained from this resin composition in which at least one surface of the molded article is a polypropylene layer having the substantially syndiotactic structure.

This application is a divisional of application Ser. No. 08/124,531,filed Sep. 22, 1993, now U.S. Pat. No. 5,637,367, which is acontinuation of application Ser. No. 07/831,519, filed Feb. 5, 1992, nowabandoned.

BACKGROUND OF THE INVENTION

(i) Field of the Invention

The present invention relates to molded articles of a polypropylenewhich are transparent and excellent in impact resistance. Morespecifically, it relates to transparent and impact-resistant moldedarticles obtained by blow molding a polypropylene having a substantiallysyndiotactic structure, or a composition comprising a polypropylenehaving a substantially syndiotactic structure and a copolymer ofethylene and propylene as well as transparent multi-layer moldedarticles having good impact-resistance which are obtained from theabove-mentioned composition and in which at least one surface of eacharticle has a polypropylene layer having a substantially syndiotacticstructure.

(ii) Description of the Prior Art

A syndiotactic polypropylene has been known for a long period of time.However, a polypropylene obtained by polymerization at a low temperaturein the presence of a conventional catalyst comprising a vanadiumcompound, an ether and an organic aluminum compound is poor insyndiotacticity. Therefore, the thus prepared polypropylene is hardlyconsidered to have characteristics of the syndiotactic polypropylene,and much less, a copolymer of ethylene and propylene which can beobtained by the use of the above-mentioned catalyst is scarcely regardedas a crystalline polypropylene.

On the contrary, a polypropylene having good tacticity, i.e., asyndiotactic pentad fraction of more than 0.7 has been discovered forthe first time by J. A. Ewen et al. which can be obtained by the use ofa catalyst comprising a transition metal compound having asymmetricligands and an aluminoxane (J. Am. Chem. Soc., 110, 6255-6256, 1988).

Molded articles which can be prepared by molding a syndiotacticpolypropylene obtained by the above-mentioned J. A. Ewen et al. methodhave good transparency and relatively excellent stiffness, but they havethe problem that their impact resistance at low temperatures is bad.

On the other hand, an isotactic polypropylene is inexpensive and good inheat resistance, and therefore it can be blow molded to manufacturebottles and the like.

However, molded articles made from the isotactic polypropylene have goodheat resistance, but they are poor in transparency and bad in impactresistance at low temperatures. Thus, for the purpose of improving theimpact resistance at the low temperatures, a block copolymer withethylene can be used, but in this case, there is the problem that itstransparency is impaired.

SUMMARY OF THE INVENTION

An object of the present invention is to provide molded articles of apolypropylene having good transparency and excellent impact resistance.

Another object of the present invention is to provide blow moldedarticles of a polypropylene which are excellent in transparency andimpact resistance.

Still another object of the present invention is to provide multi-layermolded articles of a polypropylene which are excellent in transparency,impact resistance and surface hardness.

The other objects of the present invention will be apparent fromdescription given hereinafter.

The above-mentioned objects of the present invention have been achievedby the following molded articles of a polypropylene:

Transparent impact-resistant molded articles obtained by blow molding apolypropylene having a substantially syndiotactic structure, or a resincomposition containing a polypropylene having a substantiallysyndiotactic structure and a copolymer of ethylene and propylene.

Transparent and impact-resistant multi-layer molded articles having goodstiffness which is obtained from a resin composition containing apolypropylene having a substantially syndiotactic structure and acopolymer of ethylene and propylene, at least one surface of eacharticle being a layer of the polypropylene having the substantiallysyndiotactic structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A polypropylene having a substantially syndiotactic structure can beobtained by, for example, the above-mentioned Ewen et al. method. Asuitably usable catalyst is a catalyst system comprising a transitionmetal compound having asymmetric ligands such asisopropyl(cyclopentadienyl-1-fluorenyl)hafnium dichloride orisopropyl(cyclopentadienyl-1-fluorenyl)zirconium dichloride and analuminoxane which are disclosed in the above-mentioned J. A. Ewen et al.literature. An example of the aluminoxane is what is obtained bycondensing an alkylaluminum with water to have a polymerization degreeof preferably 5 or more, and more preferably 10 or more.Methylaluminoxane having the above polymerization degree is preferablyused.

Another catalyst having a structure which is different from that of theabove-mentioned catalyst can also be utilized in the present invention,so long as it can provide a homopolymer having a relatively hightacticity, i.e., a syndiotactic pentad fraction of 0.7 or more when usedto prepare the homopolymer of propylene A. Zambelli et al.,Macromolecules, 6, 925 (1973) and ibid., 8, 687 (1975)!. For example, acatalyst comprising a transition metal compound having asymmetricligands and a organic aluminum compound is effective.

The amount of the aluminoxane is from 10 to 1,000,000 mole times,particularly from 50 to 5,000 mole times as much as that of thetransition metal compound having the asymmetric ligands. Furthermore, inthe case that the organic aluminum compound is used, the amount of thiscompound is preferably from 0.1 to 100,000 mole times, more preferablyfrom 1 to 10,000 mole times as much as that of the transition metalcompound.

No particular restriction is put on a polymerization process, and therecan be utilized a solvent polymerization process using an inert solvent,a bulk polymerization process in which there is substantially no inertsolvent, or a gas phase polymerization process.

Usually, the polymerization temperature is from -100° to 200° C. and thepolymerization pressure is from atmospheric pressure to 100 kg/cm²(gauge pressure).

Preferably, the temperature is from -100° to 100° C. and the pressure isfrom atmospheric pressure to 50 kg/cm² (gauge pressure).

Propylene can be polymerized alone or copolymerized with 10% or less ofethylene or an α-olefin having 4 or more carbon atoms, preferably 4 to20 carbon atoms such as butene-1, pentene-1, hexene-1, heptene-1 or4-methylpentene-1. When the ratio of the above-mentioned ethylene orα-olefin is in excess of 10% by weight, the characteristics of moldedarticles obtained from this copolymer, or the resin compositioncontaining the ethylene-propylene copolymer deteriorates unpreferably.

In the case that the polypropylene having a substantially syndiotacticstructure is a homopolymer of propylene, its syndiotactic pentadfraction preferably is 0.6 or more, more preferably 0.7 or more. Whenthe pentad fraction is 0.6 or less, characteristics of the crystallinepolypropylene are not sufficient and physical properties areunpreferably poor.

In the case of the copolymer of propylene and ethylene or the otherα-olefin, the copolymer is such that in the absorption spectrum of ¹³C-NMR measured in a 1,2,4-trichlorobenzene solution, a peak intensityobserved at about 20.2 ppm is 0.3 or more, preferably 0.5 or more of apeak intensity attributed to all the methyl groups of the propyleneunit. When this ratio is 0.3 or less, physical properties areunpreferably poor.

The molecular weight of the polypropylene having the substantiallysyndiotactic structure is such that its intrinsic viscosity measured ina tetrahydronaphthalene solution at 135° C. is from 0.1 to 20,preferably from 0.5 to about 10.0.

The ethylene-propylene copolymer preferably contains 10 to 95% by weightof ethylene. When the copolymer having an ethylene content outside thisrange is blended with the polypropylene having a substantiallysyndiotactic structure, the improvement effect of impact resistancecannot be obtained. Above all, the ethylene content is preferably from15 to 90% by weight. In this copolymer, 50% or less of ethylene can bereplaced with α-olefin having 4 or more carbon atoms.

The above-mentioned copolymer preferably has a glass transitiontemperature of -10° C. or less, more preferably -20° C. or less. Anparticularly preferable example of the copolymer is such a copolymer asto be sufficiently compatible with the polypropylene having asubstantially syndiotactic structure or such a copolymer as to bedispersible as fine particles in the syndiotactic propylene. Theabove-mentioned sufficiently compatible copolymer has propylene chainsin a racemic state. The degree of this racemic state can be representedby a racemic fraction of a serial of 2 or 3 propylene monomers, when 6monomer units in the polymer chain are observed, and this structure canbe elucidated by ¹³ C-NMR. For example, this detail has been reported inAsakura et al. Polymer, 129, 2208 (1988)!. Furthermore, theabove-mentioned copolymer which is dispersible as fine particlespreferably has a relatively low melt viscosity and is dispersible in thestate of fine particles smaller than the wave length of visible lightwhen mixed.

Such a copolymer can be prepared by the use of a certain kind ofcatalyst such as a titanium compound-containing catalyst, a vanadiumcompound-containing catalyst or a metallocene-containing catalyst. Thecopolymer is also commercially available under various trademarks.

The molecular weight of this copolymer is such that its intrinsicviscosity measured in a tetrahydronaphthalene solution at 135° C. ispreferably from 0.1 to 20, more preferably from 0.5 to 10.

In the resin composition comprising the polypropylene having asubstantially syndiotactic structure and the copolymer of ethylene andpropylene, the weight ratio of the polypropylene to the copolymer ispreferably not less than 30/70, more preferably not less than 45/55, andthe upper limit of the weight ratio is preferably 99/1.

When the above-mentioned weight ratio is less than 30/70, the moldedarticles obtained from such a resin composition are poor in stiffness.

When the upper limit of the weight ratio is in excess of 99/1, themolded articles obtained from such a resin composition scarcely exertthe improvement effect of impact resistance, and the impact resistanceof these molded articles is substantially equal to that of moldedarticles obtained from the polypropylene having a syndiotacticstructure.

The particularly preferable weight ratio is present in the range of from55/45 to 98/2.

The resin composition which can be used in the present invention can beprepared by mixing the polypropylene having the substantiallysyndiotactic structure and the copolymer of ethylene and propylene inthe above-mentioned ratio by the use of a kneader which can achieve goodmixing. Alternatively, the resin composition can be obtained by theso-called block copolymerization process which comprises firstpolymerizing propylene to form the polypropylene having a substantiallysyndiotactic structure, and then copolymerizing ethylene and propylenein this polymerization system. A method which can provide better resultscomprises vigorously kneading the copolymer having racemic propylenechains with the polypropylene having the substantially syndiotacticstructure.

As the above-mentioned kneader, there can be used a kneader which cancarry out relatively vigorous kneading, for example a twin-screwextruder or a Bumbury's kneader. A kneading temperature is preferablyfrom 150° to 350° C., more preferably 180° to 300° C. In the case thatthe copolymer in which the propylene chain is racemic is kneaded withthe polypropylene having the substantially syndiotactic structure so asto obtain the good results, a glass transition temperature is measuredby analyzing dynamic visco-elasticity, and the kneading operation shouldbe carried out until the transition attributed to the ethylene-propylenecopolymer is not observed any more. Here, the observation of notransition means that a peak of tan δ attributed to the copolymer ofethylene and propylene decreases to about 1/3 of a value before thekneading, when the measurement is made by a dynamic mechanical thermalanalysis.

The thus obtained resin composition, or a polypropylene having asubstantially syndiotactic structure is then blow molded. In the presentinvention, any blow molding process can be employed, so long as itbasically comprises the steps of forming a parison, feeding the same toa mold, injecting compressed air or the like thereinto, and then blowingit. Particularly, with regard to the formation of the parison, variousimproved processes are known, and they can be employed in the presentinvention. For example, there are a process of molding the material intoa cylindrical form by extrusion molding, and then blowing it; a processof cooling and cutting the cylindrical material, and then heating andblowing it; and a process of molding the material into a cylindricalform by injection molding, and then blowing it.

The molded articles which are obtained from the resin compositioncomprising the polypropylene having the substantially syndiotacticstructure and the copolymer of ethylene and propylene are excellent inimpact resistance at low temperatures, but they have the problem thatsurface hardness is slightly poor. This problem can be solved byallowing at least one surface of the molded article from theabove-mentioned resin composition to be made from the polypropylenehaving the substantially syndiotactic structure.

No particular restriction is put on a method for preparing suchmulti-layer molded articles, and a suitable method such as multi-layerblow molding, multi-layer injection molding or multi-layer extrusion canbe employed. Here, it is important that the surface on which hardness isrequired is made from the polypropylene having the substantiallysyndiotactic structure. A particularly preferable example of thepolypropylene having the substantially syndiotactic structure is apropylene homopolymer having such a structure.

The thickness ratio of the layer of the above-mentioned resincomposition to the layer of the polypropylene is preferably in the rangeof from 1/1 to 1/0.001, more preferably from 1/0.5 to 1/0.05 in view ofthe improvement of the impact resistance at low temperatures.

In the case of molded articles such as bottles which can be obtained byblow molding, only the outer layers of these molded articles may be madefrom the polypropylene having the substantially syndiotactic structureand the inner portions thereof may be free from the polypropylene layerhaving the substantially syndiotactic structure.

The molded articles according to the present invention are excellent intransparency and luster regarding appearance, and they are alsoexcellent in impact resistance. In addition, they are also excellent insurface hardness, if they are prepared in the form of multi-layer moldedarticles.

The present invention will be described in reference to examples andcomparative examples. It should be noted that the scope of the presentinvention is not limited to these examples.

In the examples, G at the rear of pressure values represents a gaugepressure, and wt. % means % by weight.

EXAMPLE 1

(a) 15 mg of isopropyl(cyclopentadienyl-1-fluorenyl)zirconium dichlorideand 2 g of methylaluminoxane (polymerization degree 16.1) made by TosoAkzo Co., Ltd were dissolved in 3 liters of toluene in a 7-literautoclave. This isopropyl(cyclopentadienyl-1-fluorenyl)zirconiumdichloride was obtained by converting, into a lithium salt,isopropylcyclopentadienyl-1-fluorene synthesized in an ordinary manner,reacting the same with zirconium tetrachloride, and then recrystallizingthe resultant reaction product. Afterward, propylene was fed to theautoclave at 20° C., until a pressure of 4 kg/cm² -G was attained, andpolymerization was then carried out for 1 hour, while propylene wasadditionally fed so as to keep up 4 kg/cm² -G. Next, propylene waspurged from the autoclave, until 0.5 kg/cm² -G was attained. A part ofthe resultant slurry was sampled, filtered, and then dried to obtain apolymer, and this polymer was dissolved in 1,2,4-trichlorobenzene andthen analyzed by ¹³ C-NMR. As a result, the ratio of syndiotactic pentadwas 0.93.

(b) Ethylene was added to the autoclave so as to be 3 kg/cm² -G, andpolymerization was then carried out for 20 minutes. After completion ofthe polymerization, the unreacted monomer was purged, and the resultingpolymerization mixture was filtered to obtain a powder. This powder waswashed 5 times with 1 liter of hexane every time, and then dried at 80°C. under reduced pressure to obtain 220 g of a polymer. Afterward, thispolymer was analyzed by ¹³ C-NMR, and as a result, the content ofethylene in the polymer was 12.4 wt. %, and the ratio of thesyndiotactic pentad was 0.78. Furthermore, an intrinsic viscosity(hereinafter referred to as "η") measured in a tetrahydronaphthalenesolution at 135° C. was 1.24, and a ratio of the weight averagemolecular weight to the number average molecular weight of the polymer(hereinafter referred to as "MW/MN") measured in a1,2,4-trichlorobenzene solution at 135° C. was 6.7. The ratio of theethylene-propylene copolymer to the total polymer was calculated fromconcentrations of the slurries before and after the commencement of thecopolymerization of ethylene and propylene, and as a result, this ratiowas 32 wt. %. In consequence, it can be presumed that the ethylenecontent in the copolymer was 41 wt. %.

(c) The thus obtained polymer was further kneaded at 210° C. by means ofan extruder having a cylinder diameter of 30 mm made by Ikegai IronWorks, Ltd., and it was then molded at a parison molding temperature of195° C. and at a mold temperature of 20° C. at the time of blowing by ablow molding machine made by Placo Co., Ltd. to prepare a blown bottleof an internal volume of 750 ml. For the thus molded article, haze (%)was measured in accordance with ASTM D1003, and Izod impact strength(kg·cm/cm) was measured in accordance with ASTM D256 (23° C., -10° C.)for samples which were prepared by cutting the blown bottle. As aresult, Metsuke (the weight of the blown bottle) was 41 g, the haze was12.4%, and the Izod impact strength was 58 and 49 kg·cm/cm,respectively.

EXAMPLE 2

(a) Propylene was polymerized by the same procedure as in Example 1 (a)to obtain a polymer having η of 1.38, a syndiotactic pentad ratio of0.93, and MW/MN of 2.1. Next, this polymer was molded in the samemolding manner as in Example 1 (c) to obtain a blown bottle. Physicalproperties of this blown bottle were as follows: Metsuke was 37 g, hazewas 10.8%, and Izod impact strength was 58 and 3.5 kg·cm/cm,respectively.

(b) A catalyst obtained in Example 1 (a) was used, and propylene was fedto an autoclave until 0.5 kg/cm² (gauge) was attained and ethylene wasfed thereto until 3 kg/cm² was attained. Polymerization was then carriedout to prepare a copolymer of ethylene and propylene. η of thiscopolymer was 0.88, and an ethylene content was 45 wt. %.

(c) 30 parts by weight of this copolymer were mixed with 70 parts byweight of syndiotactic polypropylene obtained in the above-mentionedparagraph (a) by the use of the same extruder and in the same manner asused in Example 1 (c) to obtain a composition. Next, this compositionwas molded into a blown bottle. With regard to physical properties ofthis blown bottle, Metsuke was 42 g, haze was 12.1%, and Izod impactstrength was 58 and 59 kg·cm/cm, respectively.

EXAMPLE 3

70 parts by weight of a polymer obtained in Example 2 (a) were mixedwith 30 parts by weight of Tafmer (trademark) SPO370 (η was 1.41, and anethylene content was 70.6 wt. %) made by Mitsui PetrochemicalIndustries, Ltd. which was a random copolymer of ethylene and propylenein the same manner as in Example 2 (a) to obtain a composition. Next,this composition was molded into a blown bottle in the same manner as inExample 1. With regard to physical properties of this blown bottle,Metsuke was 49 g, haze was 13.1%, and Izod impact strength was 61 and 63kg·cm/cm, respectively.

Comparative Example 1

A commercially available isotactic polypropylene (MJS 5.1 made by MitsuiToatsu Chemicals, Inc.; a random copolymer of propylene and ethylenehaving an ethylene content of 4.9 wt.% and a melt index of 1.5 g/minute)was blow molded in the same manner as in Example 1 (c). Physicalproperties of the thus molded article were as follows:

Metsuke was 69 g, haze was 51.5%, and Izod impact strength was 48 and2.8 kg·cm/cm, respectively.

EXAMPLES 4 TO 7 AND COMP. EXAMPLE 2

A syndiotactic polypropylene obtained in Example 2 (a) was kneaded withan ethylene-propylene copolymer obtained in Example 2 (b) in ratiosshown in Table 1 in the same manner as in Example 1 (c), followed byblow molding in the same manner as in Example 1 (c). For the thusobtained blown bottles, physical properties were measured. The resultsare set forth in Table 1. In this connection, the composition ofComparative Example 2 could not be molded.

                                      TABLE 1                                     __________________________________________________________________________                          Physical Properties                                                           of Molded Articles                                      Example                       Izod Impact                                     or    Syndiotactic                                                                         Ethylene-Propylene                                                                             Strength                                        Comparative                                                                         Polypropylene                                                                        Copolymer                                                                              Metsuke                                                                            Haze                                                                             (kg · cm/cm)                           Example                                                                             (pts. wt.)                                                                           (pts. wt.)                                                                             (g)  (%)                                                                              23° C.                                                                     -10° C.                              __________________________________________________________________________    Comp. Ex. 2                                                                         20     80       --   -- --  --                                          Example 4                                                                           45     55       48   14.5                                                                             58  65                                          Example 5                                                                           80     20       43   12.3                                                                             61  55                                          Example 6                                                                           90     10       40   11.5                                                                             59  35                                          Example 7                                                                           98      2       39   11.5                                                                             59  21                                          __________________________________________________________________________

EXAMPLES 8 TO 11 AND COMP. EXAMPLE 3

Ethylene-propylene copolymers having ethylene contents shown in Table 2were prepared in accordance with the procedure of Example 2 (b). Eachcopolymer was kneaded with a syndiotactic polypropylene obtained inExample 2 (a) in a ratio of 50/50 in the same manner as in Example 1(c), followed by blow molding in the same manner as in Example 1 (c).Physical properties of the thus obtained blown bottles are shown inTable 2.

                  TABLE 2                                                         ______________________________________                                                       Physical Properties                                                           of Molded Articles                                             Example Ethylene Content           Izod Impact                                or      in Ethylene-Propy-         Strength                                   Comparative                                                                           lene Copolymer                                                                             Metsuke  Haze (kg · cm/cm)                      Example (%)          (g)      (%)  23° C.                                                                       -10° C.                       ______________________________________                                        Example 8                                                                             10           41       11.0 61    41                                   Example 9                                                                             30           42       12.7 59    52                                   Example 10                                                                            60           43       11.5 61    59                                   Example 11                                                                            95           46       14.5 59    45                                   Comp. Ex. 3                                                                           98           45       25.3 59    32                                   ______________________________________                                    

EXAMPLE 12

A polymer obtained in Example 1 (b) was kneaded in the same manner as inExample 1 (c), and the polymer was then blow molded at a parison moldingtemperature of 195° C. and at a blow mold temperature of 20° C. by theuse of a multi-layer blow molding machine made by Placo Co., Ltd., anouter layer of an article to be molded being made from a syndiotacticpolypropylene obtained in Example 2 (a), and an inner layer being madefrom the above-mentioned polymer. With regard to physical properties ofthe thus obtained blown bottle of an internal volume of 750 ml, Metsukewas 41 g, haze was 12.4%, Izod impact strength was 58 and 49 kg·cm/cm,respectively, and surface hardness was 51 gf. Furthermore, according toobservation and calculation of a sectional view of a specimen preparedby cutting the bottle, the thickness of the outer layer was 0.15 mm, andthat of the inner layer was 0.6 mm.

In addition, for the blown bottle obtained in Example 1, surfacehardness was measured. As a result, it was 23 gf.

EXAMPLE 13

30 parts by weight of an ethylene-propylene copolymer obtained inExample 2 (b) were kneaded with 70 parts by weight of a syndiotacticpolypropylene obtained in Example 2 (a) in the same manner as in Example1 (c), thereby obtaining a resin composition. This resin composition wasthen molded in the same manner as in Example 12 to obtain a blownbottle, the inner layer of this bottle being made from theabove-mentioned resin composition. With regard to physical properties ofthe thus obtained blown bottle, Metsuke was 42 g, haze was 12.1%, Izodimpact strength was 58 and 59 kg·cm/cm, respectively, and surfacehardness was 51 gf. In this bottle, the thickness of the outer layer was0.2 mm, and that of the inner layer was 0.6 mm.

EXAMPLE 14

The same procedure as in Example 12 was effected except that a resincomposition in Example 3 was used as an inner layer, thereby molding amulti-layer blown bottle. With regard to physical properties of the thusmolded blown bottle, Metsuke was 49 g, haze was 13.1%, and Izod impactstrength was 61 and 63 kg·cm/cm. In this bottle, the thickness of theouter layer was 0.2 mm and that of the inner layer was 0.65 mm, andsurface hardness was 53 gf.

Comparative Example 4

For a blown bottle made from an isotactic polypropylene in ComparativeExample 1, surface hardness was measured. As a result, it was 60 gf.

In a resin composition which can be used in the present invention,various usual additives can be contained which are, for example, anantioxidant, an ultraviolet absorber, an antiblocking agent, a slipagent and a nucleating agent.

Examples of multi-layer molded articles in which at least one surface ismade from the polypropylene having a substantially syndiotacticstructure include various molded articles such as plates, extrudingmaterials, sheets, films and pipes, in addition to the blown bottlesshown in the above-mentioned examples.

What is claimed is:
 1. A transparent and impact-resistant multi-layerblow-molded article which comprises:(i) at least one layer comprising asyndiotactic propylene homopolymer which has a syndiotactic pentadfraction of 0.7 or more and an intrinsic viscosity of from 0.5 to 10measured in a tetrahydronapthalene solution at 135° C. or a syndiotacticpropylene copolymer which contains 10% by weight or less of ethylene orα-olefin units having 4 to 20 carbon atoms, and wherein a peak intensityobserved at about 20.2 ppm in the absorption spectrum of ¹³ C-NMRmeasured in a 1,2,4-trichlorobenzene solution of the polypropylene is0.5 or more of a peak intensity attributed to all the methyl groups ofthe propylene unit and a copolymer of ethylene and propylene; and (ii)at least one surface layer comprising a syndiotactic propylenehomopolymer which has a syndiotactic pentad fraction of 0.7 or more andan intrinsic viscosity of from 0.5 to 10 measured in atetrahydronaphthalene solution at 135° C.
 2. The molded articleaccording to claim 1 wherein the content of the polypropylene having thesubstantially syndiotactic structure is from 30% by weight to 99% byweight of the resin composition.
 3. The molded article according toclaim 1 wherein the content of the polypropylene having thesubstantially syndiotactic structure is from 45% by weight to 99% byweight of the resin composition.
 4. The molded article according toclaim 3 wherein the content of the polypropylene having thesubstantially syndiotactic structure is from 55% by weight to 98% byweight of the resin composition.
 5. The molded article according toclaim 1 wherein the polypropylene having the substantially syndiotacticstructure is a homopolymer of propylene which has a syndiotactic pentadfraction of 0.7 or more and an intrinsic viscosity of from 0.5 to 10measured in a tetrahydronaphthalene solution at 135° C.
 6. The moldedarticle according to claim 1 wherein the polypropylene having thesubstantially syndiotactic structure contains 10% by weight or less ofethylene or α-olefin units having 4 to 20 carbon atoms, and a peakintensity observed at about 20.2 ppm in the absorption spectrum of ¹³C-NMR measured in a 1,2,4-trichlorobenzene solution of the polypropyleneis 0.5 or more of a peak intensity attributed to all the methyl groupsof the propylene unit.
 7. The molded article according to claim 1 inwhich the glass transition temperature of the ethylene-propylenecopolymer is -10° C. or less, and the ethylene-propylene copolymer issufficiently compatible with the polypropylene having the substantiallysyndiotactic structure or dispersible as fine particles in thepolypropylene having the substantially syndiotactic structure, and hasan intrinsic viscosity of from 0.5 to 10 measured in atetrahydronaphthalene solution at 135° C.
 8. The molded articleaccording to claim 1 wherein an ethylene content in theethylene-propylene copolymer is from 10% by weight to 95% by weight ofthe copolymer.
 9. The molded article according to claim 1 wherein anethylene content in the ethylene-propylene copolymer is from 15% byweight to 90% by weight of the copolymer.
 10. The molded articleaccording to claim 1 wherein the layer of the polypropylene having thesubstantially syndiotactic structure is a propylene homopolymer havingthe substantially syndiotactic structure.
 11. The molded articleaccording to claim 1, wherein said surface layer (ii) is an outer layer.